Mechanisms by which higher organisms (1) acquire, (2) maintain and (3) transmit organ-specific genetic programs mitotically are unknown. The general problem is approached using the alcohol dehydrogenase (ADH) gene-system in maize, which embraces two unlinked but coordinately regulated genes. Both Adh genes are expressed during induction by anaerobiosis, but only one gene is induced with plant growth hormones. Further, organ-specific Adh balances are regulated by a compensatory mechanism. The mechanisms underlying organ-specific gene-balance and inducibility will be sought, and the importance of transcriptional fine control will be assessed. A long-range and agriculturally significant objective is to establish totipotent maize calli. Three complementary approaches will be utilized: biochemical, genetic and embryological. (1) Biochemical probes, including heavy isotopes, 5-fluorouracil and 6-methylpurine, will be used to distinguish between pre-transcriptional, transcriptional and post-transcriptional mechanisms. Also, the feasibility of direct ADH-mRNA assays using antibody-polysome precipitation will be evaluated. (2) An efficient Adh-system mutation-recovery program is proposed; both Adh genes and ADH balance are monitored. (3) Use of in vitro organogenesis in totipotent maize callus cells is a long-range strategy; the necessary technologies will be developed. BIBLIOGRAPHIC REFERENCES: Freeling, M. and E. Brown, 1975. In situ staining of pollen grains for alcohol dehydrogenase activity. Maize Genet. Coop. News Lett. 49, 19-21. Freeling, M., 1975. Further studies on the balance between Adh1 and Adh2 in maize: gene competitive programs. Genetics 81 (4), in press.